Intra-Discal Vacuum Phenomenon (IDVP) represents an intradiscal nitrogen gas accumulation where a cavity opens in a supine position, lowering intra-discal pressure and generating a bubble. IDVP has been observed in up to 20% of elderly patients and reported in almost 50% of chronic LBP patients. With a highly accurate detection on CT, its significance lacks clarity and consideration within normative data. IDVP occurs with patterns of lumbar and/or lumbopelvic morphology and associated diagnoses. Over-60s population based sample of 2020 unrelated CT abdomen scans without acute spinal presentations, with sagittal reconstructions, inclusive of T12 to femoral heads, were analyzed for IDVP and pelvic incidence (PI). Subjects with diagnostic morphological associations of the lumbar spine, including previous fracture, autofusion, transitional vertebra and listhesis, were selected out and analyzed separately. Subjects were then equally grouped into low, medium and high PI. Prevalence of lumbar spine IDVP is 41.3%. 125 cases were excluded. 1603 subjects yielded 663 IDVP. This was increased in severity towards the lumbosacral junction (L1L2 9.4%, L2L3 10.9%, L3L4 13.7%, L4L5 19.9%, L5S1 28.5%) and those with low PI, while distribution was more even with high PI. 292 had positive diagnostic associations, which were more likely to occur at the level of isthmic spondylolisthesis, adjacent to a previous fracture or suprajacent to lumbosacral transitional vertebra (p<0.05).

This study has identified normative values for prevalence and severity of IDVP in a normal aging population. Morphological patterns that influence the pattern of IVDP such as pelvic incidence and diagnostic associations provide novel insights to the function of the aging spine.